The present invention relates generally to hydraulic pumps and more particularly to a hydraulic pump that may be operated without the need for added lubrication or atomized oil in the air source.
The prior art has included a number of rotating and reciprocating air motors useable to drive hydraulic pumps and the like. One such air motor is described in U.S. Pat. No. 3,272,081 (Vedder, et al.) entitled Air Motor, the entirety of which is expressly incorporated herein by reference.
One drawback associated with at least some of the reciprocating air motors of the prior art, including that described in U.S. Pat No. 3,272,081, is that slide valve(s) within the air motor ride in metal to metal contact with valve sleeve(s) or other parts of the apparatus and continual lubrication must be dispensed into such metal to metal interface to avoid excessive wear of the piston(s) and to maintain a reasonable service life for the air motor. Additionally, the slide valve(s) and sleeve(s) or other parts between which the metal to metal fit is required must be precisely machined for a high tolerance fit and are typically required to be made of hard, machinable metal such as stainless steel. The application of lubricant upon the engaged metal surfaces was typically accomplished by atomizing oil in the air that is used within the air motor such that the atomized oil will deposit on the piston(s) and other parts of the air motor apparatus that frictionally interface with the piston(s). However, when the air exhausts from the air motor, some amount of atomized oil typically remains in the exhausted air and presents a health risk to workers who incur long term respiratory exposure to the air/atomized oil that is exhausted by the air motor. Additionally, the use of atomized oil in the air can be laborious, cumbersome and adds expense to the operation in which it is used.
In view of the foregoing, there exists a need in the art for the development of an oilless reciprocating air motor of the type described in U.S. Pat. No. 3,272,081 wherein self lubricating or lubricious materials are positioned between the slide valve(s) and valve sleeve(s) or other portions of the air motor that frictionally interface with the slide valve(s), thereby eliminating the need for precisely machined, high tolerance fits between such parts and also eliminating the need for the use of atomized oil, other added oil or grease or added lubricant during routine operation of the air motor.
The present invention comprises an oilless air motor that is useable in a variety of applications, including the driving of a reciprocating pump component such as the ram or piston of a hydraulic pump.
In accordance with this invention, there is provided an air motor comprising a body having a bore, an air cylinder that extends from said body and opens to said bore, a first manifold, a second manifold, a third manifold, an air inlet port that leads to the first manifold, an air exhaust port that leads to the second manifold, and at least one passageway that leads from the third manifold and opens into the upper end of the air cylinder, an air piston in said cylinder provided with a hollow stem operative in the body bore and having ports opening through the bottom thereof, a slide valve sleeve disposed in the bore about the air piston, slide valve sleeve being moveable between an upper position and a lower position, slide valve sleeve providing communication (i) between the air inlet and the body bore and between the air exhaust and the upper portion of the air cylinder via the passageway, when the valve sleeve is in one of said positions; and, (ii) between the air inlet and the upper end of the air cylinder via the passageway and between the body bore and the air exhaust, when the sleeve valve is in the other of said positions; a pilot valve disposed within the valve sleeve, the pilot valve having an axial bore with a piston at one end, said pilot valve being shiftable by air pressure from the inlet entering the body bore, as controlled by the valve sleeve; a first check valve carried by the pilot valve to allow air to be received through the ports of the air piston; a second check valve carried by the pilot valve to allow air to pass from beneath the air piston into the body bore; and, a dry seal member disposed between the valve sleeve and a part of the air motor adjacent the valve sleeve to allow the valve sleeve to move back and forth without the need for oil or other lubricant between the valve sleeve and the part of the air motor adjacent the valve sleeve. In some embodiments, a slide valve will be positioned about the air piston and the dry seal will be disposed between the slide valve and the valve sleeve.
Further in accordance with the invention, the dry seal member may be formed at least partially of a lubricious material, such as a lubricious polymer or a graphite-containing or graphite-impregnated polymer.
Still further in accordance with the invention, a retaining apparatus such as a retaining ring that snap fits into an annular groove on the slide valve or other portion of the air motor adjacent to the valve sleeve to limit or prevent unwanted slippage or movement of the dry seal as the air motor operates.
Still further in accordance with the invention, there is provided a kit for replacing parts of an existing air motor that requires atomized oil or other added lubrication to eliminate the need for the continued use of atomized oil in the air or other added lubrication. Such kit may comprise a replacement air piston assembly comprising a slide valve, a valve sleeve that substantially surrounds the slide valve and a dry seal formed of lubricious material and disposed between the slide valve and the valve sleeve to prevent direct friction between the slide valve and the valve sleeve.
Further aspects and elements of this invention will become apparent to those of skill in the art upon reading the detailed description that appears herebelow in reference to the accompanying drawings.